Resonant slot and dipole antennas coupled to low‐temperature‐grown GaAs photomixers have been fabricated and tested at terahertz operating frequencies. Enhanced output power is seen from the resonant structures compared to mixers coupled to broadband self‐complementary spiral antennas. Driving point impedances as high as 300 &OHgr; are attained at the resonant frequencies. These devices will be useful as fixed frequency local oscillators for submillimeter heterodyne receivers. ©1996 American Institute of Physics.